Method and apparatus of downstream service flows classification for headend cable modem

ABSTRACT

A method and apparatus of classifying downstream service flows for a cable modem is provided. A method of classifying downstream service flows, the method including: classifying a service flow based on a Quality of Service (QoS) using a destination address of an inputted packet; composing an internal header including corresponding service flow information based on the classifying of the service flow; and adding the internal header to the inputted packet.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No.10-2007-0125474, filed on Dec. 5, 2007, in the Korean IntellectualProperty Office, the entire disclosure of which is incorporated hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to downstream service flow processing in anetwork, for example, a Hybrid Fiber Coax (HFC) network, and moreparticularly, to a method and apparatus of classifying a cable modem(CM) to which a packet is transmitted, with respect to downstreampackets transmitted from a network service interface to a Cable ModemTermination System (CMTS) located in a headend, and classifying aservice flow to transmit the packet based on a classification rule of acorresponding CM.

This work was supported by the IT R&D program of MIC/IITA[2006-S-019-02, The Development of Digital Cable Transmission andReceive System for 1 Gbps Downstream].

2. Description of Related Art

A Hybrid Fiber Coax (HFC) network is a network including an opticalfiber and a coaxial cable, and is a broadband transmission network totransmit a data signal (the Internet, a cable television (TV), crimeprevention, disaster prevention, remote inspection of a meter, andautomatic control) using the optical fiber to a broadcasting station andan Optical Network Unit (ONU), and using the coaxial cable from the ONUto members.

A downstream data packet inputted using a network interface in a cablenetwork following Data Over Cable Service Interface Specifications(DOCSIS) must be transmitted to a receivable channel of a correspondingcable modem (CM) in order to transmit the downstream data packet to aspecific CM.

A channel transmittable to the corresponding CM may be one, or may be aplurality of channels when supporting channel bonding. Downstreampackets are classified into service flows in accordance with eachQuality of Service (QoS) and are scheduled to the channel transmittableto the CM.

Accordingly, a Cable Modem Termination System (CMTS) must allocate andclassify the service flows based on the QoS requested from the CM.

A single CM may admit a plurality of service flows, and a single channelmust transmit the plurality of service flows. When the CM receivesdownstream data by a plurality of channels using the channel bonding, asingle service flow may be distributed into the plurality of channelsusing a bonded channel group and be transmitted.

Accordingly, all downstream packets in the HFC network following DOCSISmust be classified into service flows and be scheduled to a channel bywhich the corresponding service flow from among various downstreamchannels of the CMTS is transmittable.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a method and apparatus ofclassifying downstream service flows which can classify a Media AccessControl (MAC) address of a cable modem (CM) to which a packet istransmitted, using a destination MAC address of downstream data packetsin an Institute of Electrical and Electronics Engineers (IEEE) 802.3MAC/DEC-Intel-Xerox (DIX) configuration, the downstream data packetstransmitted from a network interface to a Cable Modem Termination System(CMTS) in a Data Over Cable Service Interface Specifications(DOCSIS)-based cable network.

Another aspect of the present invention also provides a method andapparatus of classifying downstream service flows which can compose asearch pattern to search for a service flow using a CM MAC address andan upper data portion of an inputted packet.

Another aspect of the present invention also provides a method ofclassifying a service flow to be transmitted, the service flowcorresponding to a Quality of Service (QoS) of a downstream packet froma service flow classification table, and an information table forservice flow classification.

Another aspect of the present invention also provides a method oftransmitting service flow information to a downstream packet schedulingblock, an information table structure and relation to embody theabove-described schemes, and a structure of related materials.

According to an aspect of the present invention, there is provided amethod of classifying downstream service flows, the method including:classifying a service flow based on a Quality of Service (QoS) using adestination address of an inputted packet; composing an internal headerincluding corresponding service flow information based on theclassifying of the service flow; and adding the internal header to theinputted packet.

According to another aspect of the present invention, there is provideda method of classifying downstream service flows, the method including:extracting a destination address of an input packet; determining whetheran Ethernet MAC address of a CM to which the input packet is transmittedexists, using the destination address; composing a search characterstring based on QoS information included in the Ethernet MAC address ofthe CM and the input packet when the Ethernet MAC address of the CMcorresponding to the destination address exists; searching for areference address corresponding to the search character string andsearching for service flow information based on the retrieved referenceaddress when the reference address is retrieved; and composing aninternal header including the retrieved service flow information andadding the internal header to the input packet.

According to still another aspect of the present invention, there isprovided an apparatus for classifying downstream service flows, theapparatus including: a downstream service flow classifier to receiveservice flow information about an input packet, and to add an internalheader; a service flow classification table to receive a searchcharacter string from the downstream service flow classifier, to searchfor reference address information for searching for the service flowinformation, and to provide the downstream service flow classifier withthe retrieved reference address information; and a service flowinformation table to provide the downstream service flow classifier withthe service flow information corresponding to the retrieved referenceaddress information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the present invention will becomeapparent and more readily appreciated from the following detaileddescription of certain exemplary embodiments of the invention, taken inconjunction with the accompanying drawings of which:

FIG. 1 illustrates a downstream service flow transmission conceptaccording to an exemplary embodiment of the present invention;

FIG. 2 illustrates an apparatus for classifying downstream service flowsaccording to an exemplary embodiment of the present invention;

FIG. 3 illustrates a configuration of an input packet according to anexemplary embodiment of the present invention;

FIG. 4 illustrates a configuration example of an information table forclassifying downstream service flows according to an exemplaryembodiment of the present invention;

FIG. 5 is a flowchart illustrating a packet classification process of adownstream service flow classifier according to an exemplary embodimentof the present invention; and

FIG. 6 illustrates an output packet format of a downstream service flowclassifier according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The exemplary embodiments are described below in order toexplain the present invention by referring to the figures.

When detailed descriptions related to a well-known related function orconfiguration are determined to make the spirits of the presentinvention ambiguous, the detailed descriptions will be omitted herein.Also, terms used throughout the present specification are used toappropriately describe exemplary embodiments of the present invention,and thus may be different depending upon a user and an operator'sintention, or practices of application fields of the present invention.Therefore, the terms must be defined based on descriptions made throughthe present invention.

FIG. 1 illustrates a downstream service flow transmission conceptaccording to an exemplary embodiment of the present invention.

Referring to FIG. 1, a Cable Modem Termination System Media AccessControl (CMTS MAC) layer of a headend includes a service flowclassification unit and a scheduling and distribution unit.

The service flow classification unit includes a downstream service flowclassifier 101.

The downstream service flow classifier 101 classifies downstream datapackets 102 in an Institute of Electrical and Electronics Engineers(IEEE) 802.3 MAC/DEC-Intel-Xerox (DIX) configuration by a service flowunit, the downstream data packets 102 being transmitted from a Data OverCable Service Interface Specifications (DOCSIS)-based Hybrid Fiber Coax(HFC) network to a Cable Modem Termination System (CMTS).

The downstream service flow classifier 101 classifies a service flow 103by which a packet is served, based on a Quality of Service (QoS) of eachpacket

The scheduling and distribution unit includes a realignment unit 104 torealign downstream packets 103 classified by a downstream service forsupporting a channel bonding function and a distributor 105 to performscheduling and distribution based on a transmission policy classified bythe service flow. Here, service flow information is classified in thedownstream packets 103.

The downstream packets are distributed (106) to a downstream channel towhich the downstream packets are transmitted, based on the schedulingperformed by the distributor 105, and are transmitted to a cable modem(CM).

A configuration of an outputted packet is a frame in which a DOCSIS MACheader for transmission in the HFC network is added to an upper portionof a packet.

A method of classifying downstream service flows according to anexemplary embodiment of the present invention classifies a service flowbased on a QoS using a destination address of an inputted packet,composes an internal header including corresponding service flowinformation based on the classifying of the service flow, and adds theinternal header to the inputted packet.

FIG. 2 illustrates an apparatus 200 for classifying downstream serviceflows according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the apparatus 200 for classifying the downstreamservice flows includes a downstream service flow classifier 201, a CMMAC address search table 202, a service flow classification table 203,and a service flow information table 204.

The downstream service flow classifier 201 receives service flowinformation about an input packet, and adds an internal header.

According to an exemplary embodiment of the present invention, thedownstream service flow classifier 201 classifies a service flow withrespect to an input packet in an IEEE 802.3 MAC/DIX configurationtransmitted from a network interface based on a QoS, and transmits, to afunction block for downstream transmission scheduling, a frame in whichthe service flow information is added to the internal header.

According to an exemplary embodiment of the present invention, asillustrated in FIG. 3, a packet format of the input packet includes adestination address 301.

The packet format of the frame in which the internal header is added isillustrated in FIG. 6.

The downstream service flow classifier 201 identifies a CM including adestination node required to transmit a packet from the CM MAC addresssearch table 202 using a destination MAC address of an inputted packet,as an additional service node.

The CM MAC address search table 202 includes a CM MAC address and anEthernet MAC address with respect to service nodes included in the CM.Accordingly, the CM MAC address search table 202 is composed to searchfor the Ethernet MAC address of the CM to which the packet istransmitted, from a destination address to which the input packet istransmitted.

The downstream service flow classifier 201 identifies a header portionof the packet including a QoS classification characteristic included inthe packet with respect to a downstream packet of classifying the CM towhich the packet is transmitted, and classifies the service flow fromthe service flow classification table 203.

The service flow classification table 203 is composed to return areference address of the service flow information table 204 includingthe service flow information using input packet data and the CM MACaddress as a search word.

The downstream service flow classifier 201 adds the related service flowinformation with respect to the input packet in which the service flowis classified, as an internal header configuration, and finally outputsthe service flow information to a downstream scheduling block.

According to an exemplary embodiment of the present invention, the CMMAC address search table 202 may include an element of a ContentAddressable Memory (CAM) function to search for contents once, thecontents being intended to be retrieved, or a Ternary ContentAddressable Memory (TCAM) function to be used for a network searchengine.

According to an exemplary embodiment of the present invention, theservice flow classification table 203 is embodied using a memory of aTCAM scheme to search for contents when a data character string of aspecific location is the same.

The service flow information table 204 may be embodied as a RandomAccess Memory (RAM)-based memory to perform search using an address ofrelated information.

FIG. 4 illustrates a configuration example of an information table forclassifying downstream service flows according to an exemplaryembodiment of the present invention.

Referring to FIG. 4, a CM MAC address search table 401 provides thedownstream service flow classifier 201 with address information of a CMcorresponding to a destination address of the input packet.

The CM MAC address search table 401 may include a table to output a6-byte CM MAC address 403 to which a packet is transmitted, with respectto a destination MAC address 402 of a 6-byte input packet.

CM MAC address registration with respect to service nodes included in aCM may be embodied using presetting by an operator's request, an addresstraining function by a layer-2 (L2) protocol, and the like.

The downstream service flow classifier 201 includes a search characterstring 404 to extract and add, from an upper bit, all data areasincluding QoS information for classification from among the retrieved CMMAC address and input packet data, and to search for a service flowclassification table 405.

The service flow classification table 405 of FIG. 4 is an informationtable embodied as a TCAM scheme used for a network search engine.

The service flow classification table 405 may include a memory to outputan address of an entry located in a top address matched with theinputted search character string as a search result.

The service flow classification table 405 may include a data array 406including a search pattern and a mask array 407 of the same length as adata array to indicate locations of data bits desired to be matched fromamong data arrays as ‘1’.

The mask array 407 is composed to be the same length as the searchcharacter string 404.

A search principle using the search character string 404 outputs anaddress with respect to data in which all character strings of alocation being set as ‘1’ in the mask array from among data arrays aresame as the search character string when the search character string isinputted.

When at least one data array in accordance with the above-describedcondition exists, an address of the data array located in an upperaddress is outputted. When at least two addresses corresponding to thesearch character string 404 are retrieved, an address located in the topaddress is outputted.

When a corresponding data array does not exist, the service flowclassification table 405 outputs a search failure signal.

Address information of the data array outputted as a search result fromthe service flow classification table 405 may be used for a reference (areference address) of a downstream service flow information table 409.

Since each entry of the service flow classification table 405 is relatedwith each entry of the downstream service flow information table 409one-to-one, the address information of the data array outputted from theservice flow classification table 405 may be used for the referenceaddress.

The downstream service flow classifier 201 calculates a location of thedata array acquired by the search result of the service flowclassification table 405 using a predetermined rule, and uses thecalculated location of the data array for the address of the memory inwhich the downstream service flow information table 409 is located.

The downstream service flow information table 409 includes at least oneof information about whether a channel bonding service is supported foreach service flow, information about a DOCSIS header type to be composed(Pkt Type), a Downstream Service Identification (DSID), a priority to beapplied to transmission scheduling, and Downstream Channel (DC) listinformation to be provided with a downstream transmission service.

FIG. 5 is a flowchart illustrating a packet classification process of adownstream service flow classifier according to an exemplary embodimentof the present invention.

Referring to FIG. 5, the packet classification process of the downstreamservice flow classifier includes extracting a destination address of aninput packet in operation S501, determining whether an Ethernet MACaddress of a CM to which the input packet is transmitted exists, usingthe destination address in operations S502 and S503, composing a searchcharacter string based on QoS information included in the Ethernet MACaddress of the CM and the input packet in operation S504 when theEthernet MAC address of the CM corresponding to the destination addressexists, searching for a reference address corresponding to the searchcharacter string and searching for service flow information based on theretrieved reference address in operations S505, S506, and S507 when thereference address is retrieved, and composing an internal headerincluding the retrieved service flow information, adding the internalheader to the input packet, and transmitting a downstream packet to adownstream channel scheduling unit in operations S508 and S509.

In operation S501, when a packet in an IEEE 802.3 MAC/DIX configurationreaches from a network interface to a MAC processing unit of a headendCM, the downstream service flow classifier 201 extracts a destinationaddress field from among Ethernet MAC address fields of the reachedpacket.

In operations S502 and S503, the downstream service flow classifier 201searches for a CM MAC address search table, and determines whether acorresponding address exists.

In operation S504, when the corresponding address exists, the downstreamservice flow classifier 201 acquires a MAC address of the CM to whichthe input packet is transmitted, extracts the acquired MAC address and adata field to a set location from among tipper data fields of the inputpacket, and composes the search character string.

In operations S505 and S506, the downstream service flow classifier 201searches for the service flow classification table 405 using the searchcharacter string.

In operation S507, when a corresponding data array exists, thedownstream service flow classifier 201 extracts service flow-relatedinformation from the downstream service flow information table 409 usinga retrieved index.

In operation S508, after the downstream service flow classifier 201composes internal header information based on the service flowinformation, the downstream service flow classifier 201 adds theinternal header to an upper portion of the input packet and generatesinformation of an output packet.

In operation S509, the downstream service flow classifier 201 transmits,to the downstream channel scheduling unit, the downstream packet inwhich the internal header is added.

In operation S510, when a corresponding service flow cannot be found inoperation S506, the downstream service flow classifier 201 classifiesthe service flow as a basic service flow of the corresponding CM, andrepeatedly performs operations from operation S507 using the basicservice flow as an index of a predetermined service flow informationtable of a basic service flow information location.

Since failing in finding information of the CM to which the inputtedpacket is transmitted in operation S503 denotes a packet transmitted toan unknown address, the service flow is classified as a broadcastservice flow based on a transmission rule of IEEE 802.1 in operationS511.

Accordingly, in operation S511, the downstream service flow classifier201 repeatedly performs operations from operation S507 using the indexof the predetermined service flow information table for the broadcastservice flow.

In operations S501 through S511, even when a plurality of classifiersexists in the CM, the service flow classification process is similarlyperformed. The service flow classification process is not performedbased on a priority of a classifier until corresponding information isfound.

According to an exemplary embodiment of the present invention disposes aclassifier having a high priority in an upper location whenclassification information is inputted in the service flowclassification table. Therefore, when at least one corresponding dataarray is generated, a repeated classification process is enabled not tobe performed by outputting the data array located in the upper portioneven when the plurality of classifiers exists.

As described above, the downstream service flow classifier 201 accordingto an exemplary embodiment of the present invention composes serviceflow classification information including data acquired from the serviceflow information table, and composes the internal header.

As illustrated in FIG. 6, the packet format including the internalheader may be added to the upper portion of the input packet.

Referring to FIG. 6, information included in the internal header mayinclude DOCSIS header type information (Pkt Type) 601, a priority 602applied to transmission scheduling, a DSID 603, and DC list information604 to be provided with a downstream transmission service.

The information included in the internal header is used for determininga downstream channel to which a packet is transmitted, composing acomplete DOCSIS MAC frame, and transmitting the DOCSIS MAC frame to aCM.

An exemplary embodiment of the present invention provides a method ofclassifying a CM to which downstream data packets inputted in an IEEE802.3 MAC/DIX or IEEE 802.1P/Q configuration are transmitted from anetwork interface, a method of classifying an inputted packet into aspecific service flow based on a classification rule classified by aservice flow of a corresponding CM, a method of transmitting classifiedservice flow information to a downstream packet scheduling block of aCMTS MAC layer, and a portion with respect to a data structure to embodythe methods. A portion with respect to a control function related togeneration/deletion of the service flow and a scheme of scheduling to adownstream channel is excluded from a category of the present invention.

The method of classifying the downstream service flows according to theabove-described exemplary embodiments may be recorded incomputer-readable media including program instructions to implementvarious operations embodied by a computer. The media may also include,alone or in combination with the program instructions, data files, datastructures, and the like. The media and program instructions may bethose specially designed and constructed for the purposes of the presentinvention, or they may be of the kind well-known and available to thosehaving skill in the computer software arts. Examples ofcomputer-readable media include magnetic media such as hard disks,floppy disks, and magnetic tape; optical media such as CD ROM disks andDVD; magneto-optical media such as optical disks; and hardware devicesthat are specially configured to store and perform program instructions,such as read-only memory (ROM), random access memory (RAM), flashmemory, and the like. Examples of program instructions include bothmachine code, such as produced by a compiler, and files containinghigher level code that may be executed by the computer using aninterpreter. The described hardware devices may be configured to act asone or more software modules in order to perform the operations of theabove-described embodiments of the present invention.

According to the present invention, it is possible to simplify aconfiguration of a data information table used for packet classificationwhen classifying a packet inputted from a network interface by a serviceflow to be transmitted, and minimize a packet classification time withrespect to inputted packets.

Also, according to the present invention, it is possible to classify aservice flow based on a priority using a single search without arepeated classification process even when at least one classifier is setfor each CM.

Also, according to the present invention, it is possible to enhanceeasiness of hardware embodiment, thereby being effectively used for adownstream frame processing system composing a CMTS MAC layer.

Although a few exemplary embodiments of the present invention have beenshown and described, the present invention is not limited to thedescribed exemplary embodiments. Instead, it would be appreciated bythose skilled in the art that changes may be made to these exemplaryembodiments without departing from the principles and spirit of theinvention, the scope of which is defined by the claims and theirequivalents.

What is claimed is:
 1. A computerized method of classifying downstreamservice flows in a Cable Modem Termination System (CTMS), the methodcomprising: extracting a destination address of an input packet, whichis an Ethernet packet; determining by a processor whether an EthernetMedia Access Control (MAC) address of a cable modem (CM) to which theinput packet is addressed exists in a MAC address search table, bysearching the MAC address search table based on the destination address;composing a search character string comprising the Ethernet MAC addressof the CM retrieved from the MAC address search table and Quality ofService (QoS) information included in the input packet when the EthernetMAC address of the CM corresponding to the destination address exists inthe MAC address search table; searching, with the search characterstring, for a reference address corresponding to the search characterstring where the reference address is an index into a service flowinformation table, and searching for service flow information based onthe retrieved reference address when the reference address is retrieved;composing an internal header including the retrieved service flowinformation and adding the internal header to the input packet to form adownstream packet, wherein contents of the input packet are notmodified, and wherein the retrieved service flow information includes apriority applied to transmission scheduling of the downstream packet;and providing the downstream packet to a downstream channel schedulingunit, wherein when the Ethernet MAC address of the CM to which the inputpacket is addressed is not found in the MAC address search table, thedownstream service flow is classified as a broadcast service flow thatis associated with an index into a predetermined service flowinformation table from which broadcast service flow information isretrieved; and the retrieved broadcast service flow information isincluded in the internal header, and the internal header is added to theinput packet to form the downstream packet.
 2. The method of claim 1,wherein, when the reference address corresponding to the searchcharacter string is not retrieved, the downstream service flow isclassified as a basic service flow information, where the basic serviceflow is associated with an index into a predetermined service flowinformation table from which basic service flow information is extractedand the extracted basic service flow information is included in theinternal header, and the internal header is added to the input packet toform the downstream packet.
 3. The method of claim 1, wherein, when atleast two reference addresses corresponding to the search characterstring are retrieved, the service flow information is retrieved based onthe reference address located in a top address.
 4. An apparatus forclassifying downstream service flows, the apparatus comprising: adownstream service flow classifier to receive service flow informationabout an input packet which is an Ethernet packet, and to add aninternal header to the input packet to form a downstream packet, whereincontents of the input packet are not modified, and to provide thedownstream packet to a downstream channel scheduling unit; an addresstable to provide the downstream service flow classifier with an EthernetMAC address of a cable modem (CM) corresponding to a destination addressof the input packet; a service flow classification table to receive asearch character string comprising the Ethernet MAC address of the cablemodem (CM) and Quality of Service (QoS) information retrieved from theinput packet, from the downstream service flow classifier, where thedownstream service flow classifier searches the service flowclassification table for a reference address associated with the searchcharacter string, where the reference address indexes into an entry of aservice flow information table comprising service flow information, andto provide the downstream service flow classifier with the retrievedreference address; and a service flow information table to provide thedownstream service flow classifier with the service flow informationcorresponding to the retrieved reference address, wherein the serviceflow information includes a priority applied to transmission schedulingof the downstream packet, wherein when the Ethernet MAC address of theCM to which the input packet is addressed is not found in the MACaddress search table, the downstream service flow is classified as abroadcast service flow that is associated with an index into apredetermined service flow information table from which broadcastservice flow information is retrieved; and the retrieved broadcastservice flow information is included in the internal header, and theinternal header is added to the input packet to form the downstreampacket.
 5. The apparatus of claim 4, wherein the search character stringconsists of the address information of the CM and Quality of Service(QoS) information included in the input packet.
 6. The apparatus ofclaim 4, wherein the service flow information table includes at leastone of priority information of a service flow corresponding to thereference address information, a Downstream Service Identification(DSID), and Downstream Channel (DC) list information.
 7. The method ofclaim 1, wherein higher priority classifiers are disposed in an upperlocation of the service flow classification table.
 8. The apparatus ofclaim 4, wherein higher priority classifiers are disposed in an upperlocation of the service flow classification table.
 9. The apparatus ofclaim 1, wherein each entry of a service flow classification table has aone to one relationship with each entry of the service flow informationtable.
 10. The method of claim 1, wherein the search character stringconsists of the Ethernet MAC address of the CM and the QoS informationretrieved from the input packet.
 11. The method of claim 1, wherein thedownstream packet is formed such that the internal header is contiguouswith the input packet.
 12. The method of claim 1, wherein the downstreampacket consists of the internal header and the input packet.
 13. Theapparatus of claim 4, wherein each entry of the service flowclassification table has a one to one relationship with each entry ofthe service flow information table.
 14. The apparatus of claim 4,wherein when the reference address corresponding to the search characterstring is not found in the MAC address search table, the downstreamservice flow is classified as a basic service flow information, wherethe broadcast service flow information is associated with an index intoa predetermined service flow information table from which service flowinformation is extracted; and the extracted basic service flowinformation is included in the internal header, and the internal headeris added to the input packet to form the downstream packet.
 15. Theapparatus of claim 4, wherein the downstream packet is formed such thatthe internal header is contiguous with the input packet.
 16. Theapparatus of claim 4, wherein the downstream packet consists of theinput packet and the internal header.